PROJECT SUMMARY/ABSTRACT Localization of protein synthesis machinery and a subset of mRNA transcripts is essential for normal function and development of polarized cells, such as the neuron. During development, neurons extend along specific paths in a manner that is spatially and temporally dependent upon environmental cues. Netrin-1, a chemoattractant cue, directs neuron growth by stimulating local protein synthesis in axonal growth cones. The human chemotropic receptor, deleted in colorectal cancer (DCC), functions as the mediator for sensing netrin-1, and directly regulating protein synthesis. It accomplishes this by an unknown interaction between the intracellular C-terminal tail and protein synthesis machinery. There is a critical need to understand this regulation because synaptogenesis, nerve regeneration and commissure formation (nerve tissue connecting the hemispheres of the brain/sides of the spinal cord) are prevented when protein synthesis is inhibited or DCC acquires inhibitory mutations. The long-term goal of this project is to understand how the structure of DCC's C-terminal tail bound to translation machinery dictates the dynamics of localized protein synthesis. The objectives of this proposal are to pinpoint the interactions between the C-terminal tail and translation machinery, and determine the order of molecular events required for cue-dependent translation. This project presents a comprehensive strategy to test a series of related hypotheses regarding the objectives, using a combination of mutational analysis, mass spectrometry, binding assays, as well as in vitro and in vivo functional assays. This study is innovative because it is the first to discern the direct translational control mechanism by a chemotropic receptor, which provides both spatial and temporal precision for protein synthesis and neuronal outgrowth. The findings from this project support growing evidence of ribosome regulation by cellular proteins, and inform new opportunities to explore this type of regulation at the cell membrane.